Engetsu Island(円月島,Engetsu-tō?) is a small island off the coast of Shirahama, Wakayama Prefecture, Japan. It includes a natural arch through which seawater passes. Its official name is Takashima(高嶋?), and it is approximately 35 metres (115 ft) east-to-west, 130 metres (430 ft) north-to-south, and 25 metres (82 ft) high at the tallest.[1]

The island is largely formed of sandstone and has become less stable over time. Since July 2009, the Shirahama town government has cautioned against approaching the island because of the risk of collapse of the arch.[2]